Electric rheostat.



P'ATENTE-D OUT. 13, 1903.. L. WILSON. ELECTRIC RHEOSVTAT. APPLICATIONFILEQ APR. 6, 1903.

N0 MODEL.

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& E S S M n W UNITED STATES 'Patented October 13, 1903.

PATENT OFFICE.

LEONARD WILSON, OF PITTSFIELD, MASSACHUSETTS, ASSlGNOR TO STANLEYELECTRIC MANUFACTURING COMPANY, OF PITTSFIELD, MASSACHUSETTS, ACORPORATIONOF NEYV JERSEY.

ELECTRIC RHEOSTAT.

SPECIFICATION forming part of Letters Patent No. 741,206, dated October13, 1903.

Application filed April 6, 1903. Serial No. 151,230. (No model.)

To all whom it may concern.-

Be it known that LLEONARD WILsoN,a subject of the King of England, and aresident of Pittsfield, Massachusetts, have invented certain new anduseful Improvements in Electric Rheostats, of which the following is aspecification.

The object of my invention is to provide a rheostat which shall allowthe current passing through any electrical apparatus to be variedgradually from zero to maximum, which shall be simple and cheap inconstruction, and which shall be economical in operation.

My invention consists, broadly, in cutting out part of the resistance inseries with a circuit and simultaneously cutting in a shunt resistance,thereby effecting a saving in resistance material, while giving a veryeven adjustment of circuit strength. My invention consists also incertain details of arrangement adapted to secure this result anddescribed in the following specification.

The drawing shows diagrammatically an arrangement embodying myinvention.

In the drawing I have shown myinvention applied to the field of aseparately-excited generator; but it will be understood that myinvention is equally applicable to other electrical apparatus in whichit is desirable that the current be gradually and economically variedbetween wide limits.

Referring to the drawing, A represents the armature, and B the field, ofa separately-excited generator.

C C are the exciter bus-bars.

D and E are resistances connected at suitable intervals tocontact-buttons d (P, the, and to 6 6 &c., respectively.

ff &c., are extra contact-buttons connected to 6' e &c.

F is a contact-strip connected to f.

F is a contact-strip connected to at.

G is a rotary arm pivoted at H, connected to one end of field B andadapted to make contact with the contact-buttons and with thecontact-strips F and F.

I is a switch for opening the field and rheostat circuit.

contact with f half of E is cut out.

J is a stop for rheostat-arm G.

The operation will be obvious from the drawing and the followingexplanation. Assume, for example, that the voltage between exciterbus-bars C C is one hundred and that the values of the resistance offield B, of resistance D, and of resistance E are twenty ohms each. Nowstarting with the arm G in the position shown, field B isshort-circuited, and no current flows through it. As arm G is movedalong contacts d (1 850., and in contact with strip F theresistance-shunting field B is gradually increased and more and morecurrent flows through field B until when arm G reaches d all ofresistance D is in shunt or parallel circuit with field B and all ofresistance E is in series with the parallel circuit. The resistance ofthe circuit between bus-bars C C is now thirty ohms. The current istherefore three and one-third amperes, one-half of which, or one andtwo-thirds amperes, flows through field B. As arm G moves from (1 to fand from F to F no change in re sistance takes place. Now as arm G ismoved along contacts ffi, 850., part of resistance E is gradually cutout until when arm G is in The resistance of the circuit betweenbus-bars C C is now twenty ohms. The current is therefore five amperes,one-half of which, or two and onehalf amperes, flows through field B.Now as arm G passes from f to e the connection with contact-strip F, andconsequently with resistance D, is broken, while all of resistance E isplaced in series with field B. The resistance between bus-bars C C isnow forty ohms. The current is therefore two and one-half amperes, allof which passes through field B, since field B is no longer shunted.Thus it is seen that the current through field B is not changed bymoving arm G from f to e. It will of course be understood that the stepfrom f to 6 may be so arranged as to produce a small change in thecurrent passing through field B proportionate to the other steps. Thiscould be accomplished by so arranging the contacts in relation toresistance E that a little less than half of resistance E would be cutout when arm G is in contact with f. This would be preferable inpractice; but for the purposes of this explanation the simplerarrangement is selected, the slight change suggested above being onethat will be obvious to those skilled in the art. Now as arm G is movedalong e 6 did, resistance E is gradually cut out until when arm G is incontact with e field B is connected directly across the exciter busbars.The current through field B is now five amperes, the maximum value.

It Will be obvious that it is not necessary that resistances D and E beequal to each other or to the resistance of B, but that the relativevalues of the resistances and. the number of contacts for eachresistance may be varied to suit different conditions.

I do not desire to limit myself to the particular construction andarrangement of parts herein shown, since changes therein which do notdepart from the spirit of my invention will be obvious to those skilledin the art.

Having thus fully described my invention, what I claim, and desire toprotect by Letters Patent, is-

1. In an electric rheostat, a series of contacts, resistances connectedto said contacts, contact-strips paralleling parts of said series, eachstrip being connected to one of said contacts, and a movable arm adaptedto engage said contacts and said contact-strips.

2. In an electric rheostat, two sets of resistances, a set of contactsconnected to points on the first set of resistances, a second set ofcontacts connected to points on the second set of resistances, a thirdset of contacts connected to points on part of the second set ofresistances, a contact-strip paralleling the firstnamed set of contactsand connected to one contact of the third-named set, a contact-stripparalleling the third-named set of contacts and connected to one contactof the firstnamed set, and a movable arm adapted to engage said contactsand said contact-strips.

3. In an electric rheostat, a circular row of contacts, resistancesconnected to said contacts, contact-strips concentric with said circularrow and extending through parts of the arc of said circular row, each ofsaid contactstrips being connected to one of said contacts, and arotatable arm adapted to engage said contacts and said contact-strips.

at. In combination, an electric circuit, two sets of resistances, a setof contacts connected to said resistances, and a switch-arm cooperatingwith said contacts, said switch-arm being adapted to connect step bystep one of said sets of resistances in series with said circuit, thento cut out part of said set of resistances and to connect the second setof resistances in shunt to said circuit, then to cut in again step bystep the whole of the first set of resistancesin series with saidcircuit, and

tenses then to short-circuit step by step the said sec ond set ofresistances.

5. In combination, an electric circuit, two sets of variableresistances, and a switch adapted to place one of said sets in serieswith said circuit and then to place part of the first set in series andthe second set in shuntwith said circuit.

6. In combination, constant potential mains, a resistance connected atone end to one of said mains and at the other end to a contact-strip, asecond resistance connected at one end to the second main, and at theother end to a second contact-strip, contacts connected to points onsaid resistances,an1ovable arm adapted to engage said contacts and saidcontact-strips,and an electric circuit connected at one end to one ofthe said mains and at the other end to said movable arm.

7. In combination, constant potential mains, two variable resistances,an electric circuit connected at one end to one of said mains,a movableswitch-arm connected to the other end of said circuit and adapted toconnect one of said variable resistances in series with said circuit,then to connect part of said resistance in series and the second of saidvariable resistances in shunt with said circuit, and then to connect thewhole of the first resistance in series and the second resistance inshunt with said circuit.

8. In combination, an electric circuit, variable resistances connectedto a series of contacts, and a movable switch-arm adapted to connect apart of said variable resistances in series with said circuit and thento connecta part of said resistances in series and a part in shunt withsaid circuit.

9. In an electric rheostat, two variable resistances, and a movable armadapted to connect a variable portion of one resistance in series withthe second resistance, then to connect the first resistance in serieswith the variable portion of a second resistance, then to cut out thefirst resistance, and then to cut outa variable portion of the secondresistance.

10. In combination, an electric circuit, a rheostat therefor, and aswitch adapted to place part of said rheostat in series with saidcircuit and then to simultaneously cut out part of said seriesresistance and connect part of said rheostat in shunt with said circuit.

11. In combination, an electric circuit, series and shunt resistancestherefor, and a switch adapted to cut out part of said series resistancewhen cutting in said shunt resistance.

Signed at Pittsfield,Massachusetts,tl1is 31st day of March, 1903.

LEONARD WILSON.

Witnesses:

L. A. HAWKINS, R. E. HAYNES.

